How do I remove an old acrylic neo-angle shower (3 piece)?

I have taken the top bracket off, which allowed for the door removal. I have removed 2 small screws on each of the 2 panels that mate up to the bracket that is screwed to the wall...I took pictures from the top so I could see the channels and what I had to do to release the panels from the wall. I can not tell what I need to do from the top. I am unable to free the panels from the walls even though I have run a putty knife between the panels and the wall after I removed all the caulk. I also did the same to the top of the base unit and the bottom of the walls and the walls will move rather easily if I lean against them.

The problem: I can't for the life of me figure out how to get the panels to come off the brackets that are screwed into the wall.

pics attached below

FYI I would just break them (would give me great pleasure) but not sure if the husband wants to keep them for anything. I can't ask him because this is a surprise for him!